Incineration



April 26, 1938. R w s 2,115,337

' INCINERATION Filed Dec. 4, 1936 ,2; ATTORNEY Patented Apr. 26, 1938 UNITED STATES INCINERATION George R. Lewers, Brooklyn, N. Y., assignor, by

mesne assignments, to Underpinning & Foundation Company, Inc., New York, N. Y., a corporation of New York Application December 4, 1936, Serial No. 114,124

9 Claims.

This invention relates to incineration and more particularly to improvements in tiered multiplehearth furnaces and to improvements in processes for drying and burning material bypassing it downwardly through a plurality of zones, gradually drying it in upper zones and then burning it in lower zones.

Although the apparatus and process of the present invention are suitable for use with many it kinds of material, they are of particular value in drying and burning waste material such as garbage and sewage material including sewage sludge and sewage screenings bothof which have a substantial moisture content.

The principal objects of the invention are to provide novel and advantageous forms of apparatus and processes for treatment of material of the general character specified. Another object relates to the condensation and removal of vapors from the gases passing from the drying zones to the burning zones where the material under treatment is passed downwardly through a plurality of drying zones and then through a plurality of burning zones. A further object relates to improvements in the heating within a multiple-hearth furnace of air supplied to the furnace.

The invention may be carried out in connection with a multiple-hearth furnace divided into an upper drying section and a lower burning section by an intermediate hearth having a gas seal through which the solids are fed in correspondence with the downward discharge through the other hearths due, for example, to the action of rabbling devices supported and operated by a hol- 55 low vertical shaft. A current of heated air may be passed through the drying zones in contact with the material on the various hearths and then laden with vapors of moisture and volatile substances may be discharged therefrom. Ordiill' narily the air thus laden with vapors would be passed, either with or without reheating, into the burning section of the furnace. According to the present invention, however, vapors mixed with l the air are condensed and removed before the air 45" is introduced into the burning section.

The air to be introduced into the drying section of the furnace may be supplied through a hollow vertical shaft used in operating rabbling devices whereby the solid material on the various hearths is agitated and fed to the outlets thereof for passage downwardly through the furnace. Heretofore air supplied to the lower end of a shaft of this kind has been conducted directly through the hollow shaft to a desired point and then discharged through an outlet or nozzle into by-passed around the obstruction through a suit- 10 able heat exchanger carried by the shaft. The heat exchanger may consist of an inlet chamber or duct surrounding the shaft and communicating with the interior of the shaft below the obstruction, a discharge chamber or duct surround- 1B ing the shaft and communicating with the interior of the shaft above the obstruction, and a plurality of ducts or tubesparallel to the shaft and connecting the inlet and discharge chambers.

Other objects, features and advantages will appear upon consideration of the following detailed description and of the drawing in which the figure is a view in vertical'section of apparatus embodying a preferred form of the invention.

Referring to the drawing, the invention may be embodied in a furnace I0 provided with a top H and hearths I2, [3, l4, l5, I6 and ll, of which the hearth ll serves as a bottom of the furnace or furnace chamber.

The material to be treated may be introduced 3 into the furnace and deposited upon the uppermost hearth l2 through a hopper l8 and a chute l9 extending through the top H of the furnace and provided with a pivoted door or gate 20 normally held closed by suitable means such as a weighted arm 2|. As soon as a sufficient amount of material to overcome the action of the weighted arm 2| collects on the door or gate 28, the door swings downwardly about its pivotal support and permits the material on the door to fall to the hearth l2. 7

As illustrated, this material falls on the hearth [2 near its periphery and is worked inwardly. to a central discharge opening 22 by suitable rabbling means including one or more radial arms 23 and inclined blades 24 carried thereby. Below the hearth l2,'the hearths l3 and 15 are provided with peripheral outlets 25, the hearths l4 and it are provided with central outlets 22 corresponding with the central outlet of the hearth l2, and the lower hearth I! is provided with a single outlet or chute 26 through which the ash is discharged from the furnace. The chute 25 is preferably provided with a gas seal in theform of a pivoted door 21 normally held in closed poa IT, suitable gas seals being. provided Where the shaft 29 passes through the top, and these;

sition by a weighted arm 28.

The material on' the hearths l3, |4, |5, l6 and I1 is moved towards the corresponding outlets by suitable rabbling means similar to that used above the hearth |2, the blades 28 above the hearths l3, I5 and I! being so inclined as to carry the material outwardly to the 'peripheral outlets thereof,'a nd the blades above the hearths I4 and H5 being so inclined as to work the material to- 'ward the central opening as in the case of hearth a i The rabbling arms 23 may be supported and operated by a hollow vertical shaft 29 passing through the central parts 'of'the central outlets 22' of the hearths |2, |4 and lfi and through small openings in the top and the hearths |3, J5 and hearths. The shaft 29 may be rotated inany suitable manner as by'meansof a'bevel gear 30 thereon, abevel gear 3| ,meshingwith the bevel gear 30, and'a' pulley 32 connected with the bevel gear 3| and driven from any suitable source of power.

The furnace may be divided into an upper or drying'section and alower burning section by the hearth I3 whichpreferably'has but one outlet 25 provided with a valve or gas seal through which thefsolid material may be fed while an effective gas seal is maintained.- Although this valve may take different forms, that disclosed comprises a tube3 3 in said outlet 25, a conical valve for valve member 34 adapted. to cooperate with the lowerendfof the tube and urged to "closing position j by, suitable means which 1 may comprise a lever 35 pivoted at 36 and having a pivotal connection with the valve member .34.

The lever 35' passes through the side "of the tube 33 and through the wall of the furnace,.the outer arm being urged downwardly by a weight 31.

Division of the furnace in this way renders possible better control of the flow of air andigases.

through the various parts of the furnace.

Air may be supplied to the drying section I through the hollow shaft 29, to the lower part of which air may be supplied by a fan 38 and connecting duct 39. The air passing upthrough the furnace in the hollow shaft. will be heated by heat exchange with the contents of the burning zones and in this preheated condition may be discharged into theupper part of the drying sec-j tion through oneor more outlets or nozzles 40. Heretofore, the air has been passed through the the'hollow shaft ing zones hollow shaft from an inlet to an outlet.

- In the present instance, itfis desired to utilize ring 43 communicating with the interior of the shaft 29 below thedam-M through'one or'more' connections 44, an upper hollow ring 45 communicating with the interior of the shaft;29 abovethe dam 4| through one or more connections 46.* Hot gases of combustion, may engage the ducts-of the heat exchanger 42 at all sides and provide effective heat exchange.

7 j The usual compartment over. a burninghearth would not ordinarilybe high enough to aecomto raise the temperature toahigher V modate a heat exchanger of desired capacity. It

may therefore be convenient to utilize two com- I partments of the burning section by arranging forthe heat exchange to pass through the central outlet of a hearth having this type of outlet. 7

As herein disclosed, the heat exchanger 42 extends through the hearth I4 of which the central outlet is madelarger for this purpose. The re-' quirement for space may also be met by spacing certain hearths farther apart, thus providing higher compartments. As shown on the drawing, the compartment above the hearth I5 is of greater height'than the other compartments.

The air supplied to-the uppermostcompartment orzone of the drying section may be passed downwardly through the section, that isconcurrently with the flow of the solids, anddischarged from thelowermost'drying compartment through a duct 41 to a condenser 48. This condenser may comprise a chamber 49 with a drainage sump at its bottom discharging through'a drain or drain pipe 50, and a pipe system; or coil 5| in the chamber connected at one end with ,a supply pipe 52 and discharging; at the other end'into thesump at the "bottom of the chamber 49, the condensate and condenser water flowing away together The liquid discharged through the drain 50.

through the drain may be carried away with the sewage filtrate resulting from a preliminary dewatering of the sewage sludge, or may be returned to. the sewage stream before it reaches the filter. In this connection attention may be called to the high moisture content of the sewage sludge fedto the furnace and the resulting large 7 volume of water vaporfiowing out of the drying section with the air stream. Obviously there will be a large amount of liquid condensed in the condenser. I

Fromthe condenser, the relatively dry air is passed through a duct 53 to the burning section, preferably into the V lowermost compartment thereof. l V

The air and hot combustion gases flow upwardly through the burning section and'are dis- 7 charged therefrom, preferably from the upper-' most compartment, through a duct 54, which may lead through a suction fan to a stack.

Obviously the number of'hearths' in thedrying V and burningsections may be varied. For use in starting and whenever needed, the various compartments or zones may be provided with'burners '54 and doors 55."

It should be understood that various changes may be made and that certain features may be used without others without" departing'from the true scope and spirit of the invention. 5

-,1. In combination mm a tiered multiplehearth furnace divided into adryi'ng section and a burning sectio-nby a hearth having a gas sear through which solid material may be fed, means Having thus/described my invention,I claim:

for supplying airfto the drying section, and means 5 btu'ning section, a condenser and means for withdrawingairladen with vapors fromlthe drying section and passing it through said condenser to the burning section.

' 2. In combination with a 1 tiered multiplehearth furnace divided into a drying section and a burning section by a hearth having a gas seal" through which solid material may be fed, means for discharging hot combustion gasesfrom' the l for supplying air to upper part of the drying secf tion, and means for discharging hot combustion" gases from the burning section, a condenser and u means for withdrawing air laden with vapors from the lower part of the drying section' and passing it through said condenser to the burning section.

3. In combination with a tiered multiplehearth furnace divided into a drying section and a burning section by a hearth having a gas seal through which solid material may be fed, means for supplying air to the drying section, and means for discharging hot combustion gases from the upper part of the burning section, a condenser and means for withdrawing air laden with vapors from the drying section and passing it through said condenser to the lower part of the burning section.

4. In combination with a tiered multiplehearth furnace divided into a drying section and a burning section by a hearth having a gas seal through which solid material may be fed, means for supplying air to the drying section, and. means for discharging hot combustion gases from the burning section, a condenser and means for withdrawing air laden with vapors from the drying section and passing it through said condenser to the burning section, said condenser comprising a chamber through which the air passes, said chamber having a drainage outlet for condensed moisture, and a water duct passing through said chamber to condense moisture carried by the air and discharging through said drainage outlet with said condensed moisture.

5. In combination with a tiered multiplehearth furnace comprising upper drying compartments and lower burning compartments, and a hollow shaft supplied with air at its lower part and discharging air into a drying compartment, means for blocking the passage of air through a part of said shaft in the burning zones and a heat exchanger surrounding said shaft and bypassing air around the blocking means.

6. In combination with a tiered multiplehearth furnace comprising upper drying compartments and lower burning compartments, and a hollow shaft supplied with air at its lower part and discharging air into a drying compartment, means for blocking the passage of air through a part of said shaft in the burning zones and a multiple duct heat exchanger surrounding said shaft and by-passing air around the blocking means.

7. In combination with a tiered multiplehearth furnace comprising upper dryingcompartments' and lower burning compartments, and a hollow shaft supplied with air at its lower part and discharging air into a drying compartment, means for blocking the passage of air through a part of said shaft in the burning zones and a heat exchanger surroundingsaid shaft and by-passing air around the blocking means, said heat exchanger comprising a duct surrounding said shaft and communicating with its interior below the blocking means, a second duct surrounding said shaft and communicating with its interior above the blocking means and a plurality of ducts connecting the first and second mentioned ducts.

8. In combination with a tiered multiplehearth furnace comprising upper drying compartments and lower burning compartments, and a hollow shaft supplied with air at its lower part and discharging air into a drying compartment, means for blocking the passage of air through a part of said shaft in the burning zones and a heat exchanger surrounding said shaft and bypassing air around the blocking means, said heat exchanger comprising a duct surrounding said shaft but spaced therefrom and communicating with its interior below the blocking means, a second duct surrounding said shaft but spaced therefrom and communicating with its interior above the blocking means and a plurality of ducts connecting the first and second mentioned ducts.

9. In combination with a tiered multiplehearth furnace in which the hearths are provided alternately with central and peripheral outlets for downward passage of the solids under treatment, and a central hollow shaft receiving air at its lower part and discharging it into the furnace above an upper hearth, said shaft passing through the central parts of the central outlets of alternate hearths and with gas-seal connections through the other hearths, a heat exchanger surrounding said shaft and extending through one of said central outlets, and means for passing through the heat exchanger air supplied through said hollow shaft.

GEORGE R. LEW'ERS. 

